1. Technical Field
The technical field generally is the test of video display devices and particularly is the creation of a plurality of test patterns by a video processing unit inside a video display device.
2. Description of Related Art
Video display devices are utilized in a variety of applications within many fields of technology, which range from TV, video games, and computers, to the display of data for monitoring various occurrences or events within different environments, e.g. machining, robotics, aircraft instrument display, computer simulation and analysis, nuclear power plant monitoring and regulation, and the like.
The most commonly used video display device is a Cathode Ray Tube (CRT). The CRT uses a special-purpose electron tube in which electrons are accelerated by high-voltage anodes, formed into a beam by focusing electrodes, and projected toward a phosphorescent screen that forms one face of the tube. The CRT devices, however, are gradually being replaced by thin flat panel display devices such as liquid crystal displays (LCD), which are thinner and lighter than the CRT and therefore can be used in almost any space.
LCD devices use the property of varying light transmittance according to the level of voltage applied to the liquid crystal to display images. LCD devices have the advantage of requiring a lower voltage than that required by other types of displays. In recent years color televisions and computer monitors featuring LCD screens have become practical. LCD-based color panels typically consist of a quartz substrate having a matrix of thin film transistors (TFT) made from polycrystalline silicon, and an LCD substrate which is constructed by laminating a transparent filter glass substrate on top of the quartz substrate and sealing liquid crystal in the small gap between the quartz substrate and the glass plate. The functional characteristic of the LCD is a twisted nematic mode. For imaging applications, the active-matrix driven display circuit arrangement is advantageous because of its adaptability to large area devices and to a high density of pixels and other circuit components. Practical applications have been implemented starting with relatively small display devices.
A number of new display technologies, such as plasma, fluorescent, and organic light emitting display (OLED) devices, are currently under development and have been used in head mounted or eyeglass display devices.
The basic functions of a video display device can be tested by visual inspection of various display patterns, created to reveal possible problems. For example, convergence of red, green, and blue primaries in a color CRT can be evaluated by the position of the separate red, green, and blue dots or pixels. Other commonly tested display functions include: geometry and distortion, sharpness and resolution, screen pixel resolution, color and gray-scale, and other miscellaneous effects such as interference, interlace, and flicker.
The visual testing is usually performed at the manufacturing and repairing facilities using video generators that provide test signals and patterns. These signals and patterns are constituted in a rather complex manner with a multiplicity of test stimuli in order to make transmission of the test information most efficient and to make visual observation and evaluation as rapid as possible. Recently, software programs, such as DisplayMate (product of DisplayMate Technologies Corp., PO Box 550, Amherst, N.H. 03031) have been developed for setting up, tuning-up, calibrating, evaluating and testing video display devices at a user's location. In these cases, however, the test signals are produced from an outside source (e.g., a video generator or a computer).
U.S. Pat. No. 5,671,011 to Soon-doo Kim, which is incorporated herein by reference, describes a test pattern display apparatus and method for adjusting the display parameters of a television picture. The test pattern is stored in a font memory and can be internally generated and displayed as needed. The apparatus, however, is designed for testing traditional black-and-white or color televisions with simple bar-type test patterns.
A very significant percentage of video display devices returned for warranty repairs actually have nothing wrong with them at all. The problems that led to their return often reside in other components of the system that generate or supply signals for the video display devices, such as a video graphic card in a PC system. These “wrongfully” diagnosed devices increase the warranty cost for the manufacturers, tie up the inventory, and also cause a lot of aggravation for the customers. In addition, an end user of a video display device may need to adjust the quality of the display at user's location from time to time.
Therefore, a need exists for a method and apparatus for testing a video display device at end user's location without any additional equipment.